Sulfur effect on Mo2N/gamma-Al2O3 catalyst studied by in situ FT-IR spectroscopy

The sulfur effect of both thiophene and H2S on Mo2N/gamma-Al2O3 catalyst ha s been characterized by in situ FT-IR spectroscopy. CO adsorption was used to probe the effect of thiophene and H2S on the surface of the Mo2N/gamma-A l2O3 catalyst. The adsorbed thiophene has strong electronic interaction wit h the MozNly-Al2O3 catalyst and does not sulfide the surface of the catalys t at temperatures below 673 K, While in the presence of H-2, the surface of the Mo2N/gamma -Al2O3 catalyst can be partially sulfided by thiophene at t emperatures as low as 373 K, simultaneously the adsorbed thiophene is decom posed or hydrodesulfurized on the catalyst. H2S has stronger interaction wi th the Mo2N/gamma-Al2O3 catalyst than thiophene does and can slightly sulfi de the catalyst surface even at room temperature. The catalyst surface is d eeply sulfided by an H2S/H-2 mixture at temperatures even about 373 K. The surface of the sulfided nitride catalyst can be only partially regenerated by a renitridation using NH3 at 873 K, indicating that some formation of su lfur species on the nitrided catalyst is irreversible. However, the nitride d surface can be completely regenerated when the catalyst is first oxidized and then renitrided, The sulfur effect on a reduced passivated MozNly-Al2O 3 catalyst was also investigated. (C) 2000 Academic Press.